Transfer functions of multiple-stage amplification circuits may include poles within the frequency bandwidth of the amplification circuits. A type-I amplification circuit may have one pole within its frequency bandwidth; a type-II amplification circuit may have two poles within its frequency bandwidth; and a type-III amplification circuit may have three poles within its frequency bandwidth. When two or more poles exist within the bandwidth of an amplification circuit, the outputs of the amplification are inherently unstable. For example, switching power converters commonly include three poles within its frequency bandwidth, thereby rendering the switching power converters unstable if the switching power converters are not stabilized with stabilization measures.
One stabilization measure is frequency compensation which utilizes a loop filter such as a resistor and capacitor pair (RC) at the output of an amplifier. The loop filter essentially introduces a zero on the left-half-plane (LHP) to counter the influence of one pole, thus stabilizing the amplification circuit. As discussed further in the subsequent sections, the capacitance of the capacitor is commonly very large. A large capacitor means that the size of the capacitor is bulk. Typically, the required capacitance exceeds the upper limit that integrated capacitors (capacitors that can be fabricated on the integrated circuit chip) can provide. Therefore, external capacitors—or discrete capacitors—are used rather than integrated capacitors to minimize the area of the integrated circuit. These external capacitors complicate the circuit fabrication process.